Most of these are self-explanatory. The easiest install method is by using the official TWRP app, available on the Play Store (it requires root), but the manual fastboot or Odin methods are still available if you prefer. Check your device's page on the TWRP site before you install, in any case - some devices have certain requirements or restrictions.

The reason for the three Samsung Galaxy Grand Prime entries is for the variations of the device, with different chipsets and different carriers meaning separate builds are required. If you have a Galaxy Grand Prime, you should probably identify which version you have before proceeding, lest you damage it or even brick it permanently. Otherwise, flash away - a world of custom ROMs and kernels awaits you.